Vital-sign monitoring and spatial tracking of multiple people using a contactless radar-based sensor

Abstract

Various medical systems exist for monitoring people in daily life, but they typically require the patient to wear a device, which can create discomfort and can limit long-term use. Contactless vital-sign monitoring would be preferable, but such technology is challenging to develop as it involves weak signals that need to be accurately detected within a practical distance, while being reliably distinguished from unwanted disturbance. Here, we show that a radar-based sensor can be used to monitor the individual vital signs (heartbeat and respiration) of multiple people in a real-world setting. The contactless approach, which does not require any body parts to be worn, uses two antennas (one transmitter and one receiver) and algorithms for target tracking and rejection of random body movements. As a result, it is robust against moderate random body movements (limb movements and desk work) and can keep track of individual people during vigorous movement (such as walking and standing up).

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Fig. 1: Experimental set-up.
Fig. 2: Range and Doppler prolife methodology.
Fig. 3: People-tracking experimental results.
Fig. 4: Comparison of linear demodulation with classic phase extraction for vital signs detection.
Fig. 5: Vital-sign monitoring experimental result.
Fig. 6: Random body movement rejection experimental result.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

The authors thank all participating volunteers, and E. Hermeling, E. Wentink and B. Grundlehner for their consistent and prompt evaluation regarding the safety and ethical aspects of our experimental protocols.

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Authors

Contributions

M.M. conceived and designed the systems and experiments, developed the range/Doppler profile methodology, analysed and interpreted the data, and wrote the paper. I.L. developed the range/Doppler profile and random body movement methodologies and processed, analysed, interpreted and plotted the data. Y.-H.L. provided technical expertise for the PLL implementation, measured the PLL phase noise and edited the manuscript. F.W. helped with designing the volunteer protocol for ethical approval, provided feedback on targeted medical applications as well as measurement validation and edited the manuscript. C.V.H. provided technical feedback, edited the manuscript and supervised the research. T.T. provided technical feedback, provided final editing of the manuscript and supervised the research.

Corresponding author

Correspondence to Marco Mercuri.

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The authors declare no competing interests.

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Supplementary Information

Supplementary Information

Supplementary Figs. 1–3

Reporting Summary

Supplementary Video

The video shows the radar Doppler signal and the extracted heartbeat and respiration signals of a sitting subject at 2.6 m who performed four different random body movements: moving an arm (at about 18 s), crossing the legs (at about 55 s), moving the torso back and forth (at about 75 s), and moving an arm (at about 105 s). The extracted biomedical signals have been compared with gold standard references (PPG and respiration belt).

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Mercuri, M., Lorato, I.R., Liu, Y. et al. Vital-sign monitoring and spatial tracking of multiple people using a contactless radar-based sensor. Nat Electron 2, 252–262 (2019). https://doi.org/10.1038/s41928-019-0258-6

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